Vehicle exhaust systems include various exhaust components that direct exhaust gases from a vehicle engine to an outlet pipe. One such component is a muffler. The muffler includes a noise attenuation valve assembly to reduce noise generated during vehicle operation. A typical muffler configuration includes an inlet pipe, an outlet pipe, and a bypass pipe. The noise attenuation valve assembly is mounted within the outlet pipe and the bypass pipe provides a bypass path for exhaust gases when the noise attenuation valve assembly is closed. Additionally, the muffler includes a resonator associated with the outlet pipe that is used to attenuate high frequency noise.
This traditional muffler outlet pipe configuration presents many assembly and manufacturing challenges. The outlet pipe includes a first tube that is formed to receive the noise attenuation valve assembly and a second tube to which a resonator shell is joined. Resonator material is wrapped around the outer circumference of the second tube and the resonator shell is then joined to the second tube such that the resonator material is positioned between the resonator shell and the second tube. The first and second tube are appropriately sized such that the first and second tubes can be joined together to form the outlet pipe. Thus, the outlet pipe must be made from multiple tubes and is subjected to many sizing and joining operations, which is disadvantageous from a material and assembly cost perspective.
The first tube also includes a mount portion to receive the bypass pipe. This mount portion is positioned perpendicularly to the first tube. The bypass pipe includes a curved end mount that is received within the mount portion of the first tube. This complicates the formation of the bypass pipe. Further, a perpendicular entry angle between the outlet pipe and bypass pipe results in high levels of flow noise generation. Thus, the traditional bypass pipe configuration is also disadvantageous from a cost and noise generation perspective.
Thus, it is desirable to provide a muffler and method for assembling a muffler that uses fewer components while also providing improved noise reduction capability.